Scientists are taking an increasingly political stance towards action on climate change. In 2005, the science academies of the G8 countries, plus China, India and Brazil, collectively called for governments to place climate change at the top of the international agenda. By 2008 they were calling for a planned transition to a low-carbon economy. Similarly, this week's international climate change conference in Copenhagen, at which I am speaking, is deliberately organised to try to influence the UN conference in December (also in Copenhagen), which will discuss placing global limits on carbon dioxide emissions. Indeed, the website calls the conference "science for politics".

Yet these are potentially dangerous times for scientists who move into political arenas. There is a serious disconnect. On one side the years drift by and we deliver our ever-starker warnings. On the other, policy-makers, business leaders and wide sections of the public barely acknowledge the dangers we face, never-mind change their actions accordingly. This can lead to desperation: how do we get people to listen?

It is tempting to try and capture people's attention with apocalyptic messages, with the media egging us on. But it's a dangerous game. Prosaically, at this week's conference every contrarian will be looking to seize on a seemingly crazy comment from a scientist to allow them to dismiss the whole conference as alarmist. Those of us concerned about climate change need to be more sophisticated in choosing how we communicate about the issue.

One example of a poor choice of facts to highlight is that the arctic sea-ice is melting and that this is bad news for polar bears. It doesn't really affect many people directly, so remains an abstract concern. However, few seem to be aware that if we continue with business-as-usual, we will push air temperatures over much of the tropics so high that it becomes physiologically very uncomfortable for humans to live there. That is, without dramatic cuts in emissions, we will condemn those 2 billion people living in the tropics to a life of daily discomfort for generations to come.

Another example is that few realise that we are changing the basic rules of agriculture. For the last 8,000 years the game has been the same: judge the likely weather based on past experience, deploy your best technology, hedge your bets, work hard, and hope that you end the year with surplus food. Increasingly the past will be a poor guide to the future, with much-increased chances of major crop failures. This is extremely worrying when we have 6.7 billion people to feed, and the recent food crisis shows the rapidity with which social unrest unfolds across the globe when food becomes expensive.

Re-focusing attention on less abstract impacts of climate change – anyone who has been to the tropics will attest that adding 5 degrees C to those alreadly high temperatures would be very unpleasant – could shift debates fast. Moreover, scientists and others concerned about climate change will also need to challenge entrenched economic ideology that is a significant barrier to tackling climate change. For example, we must challenge why complex carbon markets that have failed at EU level, and within the Kyoto protocol, are set to be replicated globally in the post-Kyoto settlement planned to be agreed in December.

Furthermore, as those who are not listened to have shown throughout history, targeted protests and civil disobedience can have a major impact. A day spent on the street, rather than in my case being in the lab, office or rainforest field site, might be my most useful service to humanity in this pivotal year. It's probably the same for the majority of us.

I know it is baffling to many that adding a few hundred parts per million to the volume of a colourless odourless gas in the atmosphere could well be our undoing. The contrarians will fill the comment boxes below this article. But is it any more fantastical than the idea that invisible things can cause us to move from being perfectly healthy one day to being dead a few days later?

Investments and actions based on the – still imperfect – scientific understanding of human physiology, diseases, their prevention and cures are probably the cause of the greatest increase in human welfare over the past two centuries. It might well be that investments and actions based on the scientific understanding of what I call the physiology of the planet are the key to human welfare in the 21st century.

The idea that bacteria cause disease took decades to move from controversial scientific hypothesis to an unquestioned fact that has radically changed our behaviour. The anti-progress voices were defeated then, and with progress in human welfare dependent upon accepting the results of the scientific method, they must be defeated again. In climate change terms we must move from residual scepticism to the implementation of solutions to energy needs without using fossil fuels at breakneck speed. A new strategic deployment of arguments, alongside precise protests to move society into a new direction, will be key ways of getting there.